The present invention relates to a throttle valve opening sensor for use with an internal combustion engine.
A conventional throttle valve opening sensor is shown in FIGS. 7 and 8 as disclosed in Japanese Laid-Open Utility Model Publication No. 59-41708. As shown in FIGS. 7 and 8, the throttle valve opening sensor comprises a substrate 1 on which an opening detecting portion 15 and a specific opening detecting portion 18 are printed, and a rotor arranged in opposed relation to the substrate 1 in such a manner as to be rotatable in association with rotation of a throttle valve. The rotor is provided with two pairs of contacts (not shown in FIG. 7). The contacts are designed to contact with the opening detecting portion 15 and the specific opening detecting portion 18, thereby detecting a throttle valve opening necessary for fuel control in engine operation and a specific opening such as an idling position. The specific opening detecting portion 18 consists of a metal conductor 19 and a collector 20 arranged inside the conductor 19. A soft glass insulator member 22 is arranged adjacent to the conductor 19, and a resistor member 21 such as a carbon resistor is arranged adjacent to the insulator member 22 for the purpose of preventing wear of the contact 10. The collector 20 consists of a metal conductor 20a formed of Ag-Pd alloy and a resistor member 20b such as a carbon resistor provided on the metal conductor 20a for the purpose of preventing migration of Ag and wear of the contact 10.
In the construction of the conventional throttle valve opening sensor, as the resistor member 20b is printed on the metal conductor 20a, an electrical contact resistance between the contact 10 and the resistor member 20b is large. As a result, a specific opening of the throttle valve such as an idling position cannot be accurately detected.